1. Field of the Invention
The present invention relates to storage systems, and more particularly, to maintaining trace information in host bus adapters (“HBAs”).
2. Background of the Invention
Storage area networks (“SANs”) are commonly used where plural memory storage devices are made available to various host computing systems. Data in a SAN is typically moved from plural host systems (that include computer systems) to the storage system through various controllers/adapters (including HBAs).
Various standard interfaces are used to move data from host systems to storage devices. Fibre channel is one such standard. Fibre channel (incorporated herein by reference in its entirety) is an American National Standard Institute (ANSI) set of standards, which provides a serial provides a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Host systems often communicate with storage systems via a HBA using the “PCI” bus interface. PCI stands for Peripheral Component Interconnect, a local bus standard that was developed by Intel Corporation®. The PCI standard is incorporated herein by reference in its entirety. Most modern computing systems include a PCI bus in addition to a more general expansion bus (e.g. the ISA bus). PCI is a 64-bit bus and can run at clock speeds of 33 or 66 MHz.
PCI-X is a standard bus that is compatible with existing PCI cards using the PCI bus. PCI-X improves the data transfer rate of PCI from 132 MBps to as much as 1 GBps. The PCI-X standard was developed by IBM®, Hewlett Packard Corporation® and Compaq Corporation® to increase performance of high bandwidth devices, such as Gigabit Ethernet standard and Fibre Channel Standard, and processors that are part of a cluster.
The iSCSI standard (incorporated herein by reference in its entirety) is based on Small Computer Systems Interface (“SCSI”), which enables host computer systems to perform block data input/output (“I/O”) operations with a variety of peripheral devices including disk and tape devices, optical storage devices, as well as printers and scanners. A traditional SCSI connection between a host system and peripheral device is through parallel cabling and is limited by distance and device support constraints. For storage applications, iSCSI was developed to take advantage of network architectures based on Fibre Channel and Gigabit Ethernet standards. iSCSI leverages the SCSI protocol over established networked infrastructures and defines the means for enabling block storage applications over TCP/IP networks. iSCSI defines mapping of the SCSI protocol with TCP/IP.
The iSCSI architecture is based on a client/server model. Typically, the client is a host system such as a file server that issues a read or write command. The server may be a disk array that responds to the client request.
HBAs today perform complex operations and are key to the overall efficiency of a SAN. HBAs may use more than one processor whose operation should be tracked to perform diagnostics in case of a failure or otherwise. HBA processors use program counters that track various processor-executed operations. However, conventional HBAs do not provide an efficient system for tracing multiple processors or providing the trace information in a user-friendly interface.
Therefore, there is a need for a system and method that can trace multiple processors in an HBA.